Specific envelope components which have been related to virulence in Haemophilus influenzae type b will be characterized. Among the six serotypes of H. influenzae, type b is most frequently associated with severe human infections. H. influenzae cultures isolated from these infections may also contain non-typable strains. The origin of many of these non-typable strains is unknown since they cannot be typed by the common methods currently used in clinical laboratories. We have recently shown by crossed and rocket immunoelectrophoresis that a non-typable strain previously thought not to possess capsular antigen does contain minimal amounts of the antigen as well as another type b specific non-capsular antigen. The above procedures will be used to examine freshly isolated H. influenzae cultures from patients for type b specific capsular and non-capsular antigens. Selected strains from the above collection will be analyzed for specific ultrastructural features already demonstrated in an encapsulated H. influenzae type b culture and two spontaneous non-typable mutants. "Unsheared" capsular antigen preparations from the encapsulated culture and mutants will be analyzed immunochemically and chromatographically for differences in their capsular antigen determinants and in molecular size. Qualitative and quantitative analyses of proteins, lipids and lipopolysaccharides of the three organisms will also be carried out. These analyses will allow detection of any differences which may be present among the cultures. By combining immunochemical and immunocytochemical methods the existence, location and chemical characteristics of the presumed specific non-capsular antigen will be undertaken. In many severe influenzal infections bacteremia persists even in the presence of high serum bactericidal titers. Recent studies have indicated that there is a host environment-mediated acquisition of phenotypic resistance in H. influenzae type b. Using the above-mentioned methods the nature of this resistance will be investigated.